use v6;

my $in = [ one => 1, two => 2, two => '2.003' ];
my %h;

for @($in) {
    if %h{.key} {
        %h{.key}.push: .value;
    } else {
        %h{.key} = [ .value ];
    }
}

say %h.perl;

# vim: ft=perl6 sw=4 ts=4 expandtab
# same output